This invention pertains to manually-operative hydraulic door closers for vertically-pivoted, swingable doors, and in particular to means for delaying the door-closing operation of such door closers.
Manually-operative hydraulic door closers known in the prior art operate to close an associated door immediately following an initial, manual opening thereof, and passage of a person through the portal or doorway. However, there are circumstances in which it is desired to delay the prompt closing of the door. For example, at exits of theaters, school buildings, sport arenas, shopping centers, factories, and the like, great numbers of people pass through a doorway at a given time. Consequently, it is unacceptable to have the door closer for the exit doors repeatedly and relentlessly endeavoring to close the exit doors with the through passage of each individual. More importantly, in heavy traffic situations, it is not acceptable for successive persons having to manually operate the hydraulic door closer and force a door open after someone has previously exited due to the door constantly going to closure after each individual passes through.
There is presently no known simple and efficient means for delaying the manually-operative, hydraulic door-closing function of a door closer for a selective and adjustable period of time, after one individual has manually operated the door closer, pushed open the door, and passed through the doorway, to render the portal fully open to others who may be following close behind. Prior art systems to address this problem have included complex circuitry and expensive components.
The foregoing describes limitations known to exist in present manually-operative, hydraulic, door closer devices. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of such limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.